It looks like we'll have everything thrown at us except the kitchen sink tonight (unless you live in Bedford). If you haven't heard, this is our first round of severe weather and spring has not officially started yet. See the bottom portion of this post for what the National Weather Service in Indianapolis is saying. Keep reading to see what I think.
I think a cold front is moving in and it is attached to the northern polar jet. The southern tropical jetstream continues to bring in warm air from the south. It looks like they will collide over southern Indiana and Kentucky tonight between 7pm and 3am. Tornadoes are possible. In fact, I saw a sounding that has a tornado right over Bedford, Indiana. The coordinates in the sounding are here.
Here is a good visual representation of the colliding air masses.
And then it looks like we get to experience this again around March 5, 2024.
If you think winter is over, think again. Check out this CFS forecast for March 29, 2024
So here is what the NWS is saying:
Area Forecast Discussion National Weather Service Indianapolis IN 1142 AM EST Tue Feb 27 2024 .Key Messages... - Record High Temperatures possible today - Strong to possibly severe weather this evening and overnight - Gusty winds this evening and overnight - Cold front arrives early Wed with brief shot of light snow - Warm temps return for the weekend && .Forecast Update... Issued at 956 AM EST Tue Feb 27 2024 Conditions are evolving as expected so far this morning following pre-dawn convection along the Ohio Valley and a few small showers passing west to east around the Spencer/Bloomington areas over the past couple hours. 993 mb surface low pressure currently positioned near the Twin Cities will drag its trailing surface trough/ pronounced cold front east across the Middle Missouri Valley today and into northwestern Illinois by 00z this evening. Central Indiana will continue to bask in the system`s warm sector, with today`s record high of 73F in jeopardy...and surpassing today`s record high maximum of 51F from 1876 likely a slam dunk through midnight tonight. Considerable cloudiness and anomalously high dewpoints now in the 55-60F range over the entire state will both inhibit the stronger warming rates seen yesterday...yet suspect continued WAA amid southerly gusts approaching 25-30 mph by early evening will boost readings to 70-75F by late day across the CWA. All convective parameters are exhibiting a potent severe potential across the region, with very high vertical wind shear over both 0-6 km and lower levels, impressive 700-500mb lapse rates, and more than adequate instability that should be blossoming through afternoon hours, especially north and west of the Indy Metro...albeit mostly elevated through daytime hours. Very latest guidance continues to delay convective initiation until this evening with a perhaps subtle yet key inversion lingering within the 750-850 mb layer. Widely scattered showers cannot be ruled out at times through the daytime hours but suspect organized thunderstorm activity to hold off until overnight hours...following removal of inversion aloft ahead of approaching frontal zone. We will continue to watch and update this dynamic situation throughout the day and tonight. && .Short Term...(Today and tonight) Issued at 256 AM EST Tue Feb 27 2024 Early this morning... Impressive moisture feed across the Ohio Valley, with several locations early this morning seeing dewpoints rise from the upper 30s to near 50 degrees. A meso-sector for satellite data has been setup over a portion of the Ohio Valley/Mid-Mississippi valley and is depicting a feed of water vapor east lifting northeast across the region. Aircraft soundings indicate the deeper moisture is still elevated at 600mb and above with a dry layer beneath this until the inversion around 850mb. Low clouds were initially progged to be expanding northeast across the area have been sluggish to expand in coverage, but latest surface obs indicate several locations upstream are beginning to see this development of a stratus deck. Winds in the near sfc layer or 0-1km show southerly flow rather uniform with very subtle deviation in the direction, and speed it also uniform between 10-15kts and gusts 15-20kts during pre-dawn hours. Some elevated reflectivity was showing up throughout Central Indiana extending west into Illinois, but this coverage is minimal and not reaching the ground at this moment. At 7Z the 925-850mb moisture transport footprint has grown with the highest values over Arkansas/Western KY/TN. This places the best gradient over Northeast Missouri where reflectivity has been expanding along the better vertical momentum. Current wind fields would suggest propagation to this area of precip would slowly slide northeast, but as eluded too earlier about aircraft soundings showing a dry wedge it may only moisten partially this layer later this morning. Midday... The big challenge for the afternoon will be how warm sfc temps can become as the sensible layer sees a surge in increase moisture. Which should slow the rate of warmth, shallow cloud layer will also play a pivotal role in max temps. But given the delay in precip development and the continued warm air advection progged, we should easily push temps back into the low 70s especially with temps pre-dawn starting in the low. Main concern for this afternoon into the evening will be focused with convective development. Looking at the setup a robust 300mb jet streak is progged to be positioned to the southwest of Central IN, placing the area within the exit region. This typically favors diffluent flow aloft, and thus in the lowest layers presence of upward motion. The limiting factors with the afternoon setup are the fact that Central IN may not be seeing the stronger sfc convergence due to more uniform wind fields from the south. A 7Z aircraft sounding indicates the inversion developing above the mixed layer, which guidance is now indicating will linger through much of the day. So despite an EML and favorable lapse rates of 7.5 to 8 C/km this afternoon, should this warn nose aloft remain for much of the day the convective footprint and upscale growth could be minimal. Should the shallow layers warm enough to erode the inversion then considerable MLCAPE in excess of 1500J/kg and effective shear within the 0-6km layer over 45kts would set the stage coupled with the aforementioned upper level jet to see robust upscale growth to convection by late afternoon leading to damaging wind/large hail and even a tornado. While the forecast is slightly more complicated, the potential remains for severe weather and thus the entire area remains in a slight risk for today. The upper level jet appears to drift further north, likely a result of the downstream height rises helping to slow the forward progression to the approaching mid-lvl trough. This will help to further sharpen the frontal boundary that will be approaching from the west late in the overnight hours. Sfc low will be zipping north into lower Michigan as the trailing cold frontal boundary will be stretching southwest through East Central IL by 6Z Wed. There remains some uncertainty tonight with how convection evolves as guidance has backed off on the convective footprint. Still some guidance indicates perhaps more linear segments develop. The atmosphere will still be conducive to seeing severe storms with the potential for slightly backed sfc winds aiding in the 0-1km helicity fields, which would support a risk for isolated rotating updrafts from the linear segment of convection pre-frontal passage. This focus would be along and east of Vincennes to Indy line. && .Long Term...(Wednesday through Monday) Issued at 256 AM EST Tue Feb 27 2024 Wednesday and Wednesday night... The long term will start off with temperatures taking a nose dive in the wake of a strong cold front that models agree will be from around in between Toledo and Cleveland to just east of Cincinnati at 12z Wednesday. This will put a temporary exclamative kibosh on the near record temperatures we experienced yesterday and will once again today. To illustrate how fast temperatures will fall during the day Wednesday, model 850 millibar temperatures at 06z Wednesday have a ridge of 13 to 15 degree C temperatures over central Indiana and by 18z Wednesday, 850 millibar temperatures are -11 degrees C over southeastern sections and -14 degrees C over northwestern sections. In addition, with the upper trough still the west and moisture slow to move out, the lingering showers will quickly mix with and change to snow before it moves southeast out of central Indiana by 18z. With deep moisture and lift through the Dendritic Growth Zone, a quick dusting of snow is possible over mainly grassy areas as the ground will start off well above freezing from the two prior abnormally warm days. High confidence with this setup that high temperatures will be right at 12z with temperatures falling through the 30s and 20s during the day. In addition, tight surface pressure gradient in the wake of the front will result in windy conditions with northwest winds gusting to 40 mph. This will make it feel like even more of a shock to the system as Wind Chills drop into the teens during the evening. Thursday through Friday night... A surface high will move across central Indiana Thursday. As it moves east of the area, during the afternoon, temperatures will start their rebound as low level flow shifts to the south. A dry column per BUFKIT soundings will allow for plenty of sunshine and low level thermals support temperatures to rebound to the upper 30s to middle 40s Thursday afternoon. Although an upper wave will move across late Friday which will bring more clouds in and potentially a few rain showers to mainly southern sections closer to better moisture, continued warm advection courtesy of breezy southerly winds will allow temperatures to climb a few more degrees into the middle and upper 40s, which is near normal for the first day of March. Saturday through Tuesday... The weekend will be looking up for outdoor enthusiasts as continued warm advection ahead of a potent and broad western system will once again result in mostly benign weather and temperatures some 15 to 25 degrees above normal.
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